DC Machine: Basic Components and Function

Basic Components of a DC Machine

Each DC machine contains two separate terminals with a magnetized center between them. There are two main parts, the stator and the rotor. The stator contains parts such as brushes, magnets and housing for the whole motor. The rotor contains the windings, the communicator and the output shaft. The two parts work together when voltage is applied to create a moving motor.

DC motors work in two directions. A DC machine that produces electricity by consuming mechanical energy is a generator. A DC motor that consumes electricity to create mechanical energy is a motor. The same basic DC machine can be either a motor or a generator.

Essential Components of a DC Machine

DC machine either uses or produces electrical energy. It does this by converting mechanical energy into electrical energy or vice versa. A DC machine is made out of two essential parts, one stationary and one moving, called the field and the armature. An essential example of a DC machine is a copper coil spinning on its own axis between two magnets. A practical DC machine also needs a commutator, brushes, poles and bearings.

1- Field (magnetic poles)

2- Armature

3- Commutator

4- Yoke and Bearings

5- Carbon Brushes of a DC Machine

1.     Field Winding of a DC Machine

• The field is the stationary part of a DC motor. A field is usually constructed out of magnetic poles. In the example above of the copper coil spinning on its own axis between two magnets, the two magnets produce a magnetic field in which a conductor, the armature, must move to produce an electric charge.
• The function of the field system is to produce uniform magnetic field within which the armature rotates.

2. Armature Winding

• The armature is the moving part of a DC motor. It moves in the field to complete the DC machine’s electro-mechanical energy conversion. In the above example, the copper coil is the armature, spinning in the magnetic field.

3. Commutator

• The spinning armature and its brushes produce an alternating electromagnetic field (EMF) that can disrupt the operation of a DC machine. A commutator in conjunction with commutating poles resolves the alternating EMF and prevents the brushes from sparking.
• It is an mechanical rectifier which converts the alternating voltage generate in armature winding into direct voltages  across the brushes. It  is made of copper segment insulated from each other by suitable insulating material and mounted on the shaft of machine.

4.   Yoke and Bearings

Every part of dc motor have its own working. As commutator, is made of to semi circular rings. Which convert ac current to the pulsating dc. And carbon brushes, which made contact  of the circuits to external source or battery. And here we also provide magnet that rotate the rotor in magnetic field to use the electrical energy or store the electrical energy. It just happen when when electric machine is used as an electric generator.

5. Carbon Brushes in a DC machine

• Brushes are used to collect the electric charge from the armature. They must be supported by brush holders. The yoke and bearings provide mechanical support to the DC machine’s spinning armature, allowing smooth, steady motion while mitigating friction.
• And purpose of carbon brushes to made the connection b/w the rotating commutator and stationary external load circuit.
• It is used to reduced sparking and provide the better connection.

The purpose of brushes is to ensure electrical connections between the rotating commutator and stationary external load circuit. The brushes are made of carbon and rest on the commutator. The brush pressure is adjusted by means of adjustable springs.

If the brush pressure is very large, the friction produces heating of the commutator and the brushes. On the other hand, if it is too weak, the imperfect contact with the commutator may produce sparking. Multi-pole machines have as many brushes as they have poles. For example, a 4-pole machine has 4 brushes. As we go round the commutator, the successive brushes have positive and negative polarities. Brushes having the same polarity are connected together so that we have two terminals viz., the +ve terminal and the -ve terminal.

Final Words

We hope you’ve liked this article on the basic function and structure of a DC machine.

You may also want to read the various function of a power system and learn software for electrical engineering.

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